Rotary pump



- Dec. 16, 1952 J. B. THOMAS ROTARY PUMP Filed Aug. 31, 1948 4 INVEN J.B THOM ATTORNEY changing the capacity of the pump.

Patented Dec. 16, 1952 UNITED STATES PATENT OFFICE Claims.

This invention relates to pumps and more particularly to a rotary pumpin which the rotor may be provided with teeth of any desired lengthwith- :in practical limits whereby the capacity of the pump may begreatly increased without materially increasing the external dimensionsthereof.

Rotary pumps of the type employing a hollow internal gear forming arotor and an idler gear having teeth meshin with the rotor havepreviously been made with the rotor machined from a solid casting orforging, it being customary to form the teeth of the rotor in a millingmachine by the use of an end mill. The faces of these teeth must beaccurately machined in order to mesh properly with the teeth of theidler gear and in order to provide an efficient pumping action. Thelength of these teeth has heretofore been limited by the end millemployed for machining the same since the depth of out which may betaken by an end mill is determined largely by the diameter of the mill,good practice dictating that this depth be not greater than twice thediameter of the mill. Attempts to use end mills of this type inmachining surfaces of gear teeth and other articles to a greater depthhave resulted in bendin or springing of the mill with consequentinaccurate surfaces being formed which in gear teeth of the typeutilized in pumps of the type with which we are here concerned wouldresult in tapered rather than parallel surfaces on the teeth, whichparallel surfaces are absolutely necessary for proper and efficientoperation of the p p.

The capacity of pumps of this type may be varied by changing thediameter of the rotor, by changing the length of the rotor, and ofcourse, within limits, by changing the speed of rotation thereof. Sincein most applications the speed of rotation is that which is optimum forthe pump employed and since the speed usually cannot readily be changed,we may for the purposes of this application disregard speed as a factorin In the majority of installations in which these pumps are employed,space is a prime factor and since the diameter of the pump must beincreased very materially in order to increase the capacity to any greatextent, it is frequently inconvenient if not impossible to incorporatepumps of sufficient diameter in a given apparatus in order to producethe capacity necessary for the operation being performed. On the otherhand, the capacity of pumps of this type may be very materiallyincreased by a comparatively small increase in the length-of the teethon the rotor, and consequently for a given increase in capacity theadditional space required when increasing this capacity by lengtheninthe teeth is considerably less than when attempting to obtain the samecapacity by increasing the diameter.

In present structures utilizing the milling machine method of formingteeth on the rotor, it is possible with a given diameter to obtain apump having capacities ranging between 5 and gallons per minute, whereasif capacities above this figure are desired it is necessary to increasethe diameter materially, which will result in an optimum capacity ofapproximately 200 gallons per minute. By utilizing longer teeth on therotor rather than increasing the diameter of the pump it is possible,and by utilizing applicant's invention practical, without materiallyincreasin the weight or size of the pump to obtain any capacity desiredbetween 90 and 200 gallons per minute. The use of longer teeth alsomaterially increases the area of tooth surface which is in frictionalcontact with the fluid being pumped and when this fluid contains a largepercentage of grit, as it does in a great many installations, the lifeof the pump is materially increased over those in which increasedcapacity is obtained by enlarging the diameter.

It is therefore an object of this invention to provide a rotary pump inWhich the capacity may be determined by providing a rotor having teethof any desired length and in'which the contour of the teeth ismaintained within the necessary tolerances thereby making possible thedesign of a pump of this type having maximum capacity butminimum sizeand weight.

It is a further object of this invention to provide a method ofconstructin a hollow internal gear type pump rotor having teeth of anydesired length and in which the surface contour of the teeth may bemaintained within the necessary manufacturing tolerances.

Further objects and advantages of the invention will be apparent fromthe following description taken in conjunction with the accompanyigndrawings, wherein:

Fig. l is a perspective view of a rotary .pump incorporating the rotorof this invention and with parts broken away for greater clarity;

Fig. 2, a sectional view in elevation showing a rotor of the typepreviously used in rotary pumps;

Fig. 3, a top plan view of a rotor constructed in accordance with thisinvention;

Fig. 4,'an elevational view in section taken on theline 4-4 of Fig. 3and showing the manner of securing the rotor teeth in position; and,

Fig. 5, a perspective View of a tooth prior to assembly with the rotor.

With continued reference to the drawing, there is shown in Fig. 1 arotary pump I!) having a base II, a discharge outlet I2 and an inlet notshown. The pump I is provided with a generally circular casing I3provided with a fixed rear wall I4 and a removable front wall I5 whichmay be secured in place by screw threaded fasteners or the like I6.Internally of the casing I3 there is provided a rotor I! havin aplurality of gear teeth I8 projecting from and secured to a driven plateI9. Plate I9 is maintained on and driven from a shaft rotatablysupported in the rear wall M of the housing I3, a suitable bearing andstufling box being provided therefor. Teeth I8 are machined to form aninternal gear and these teeth are designed to mesh with the teeth 29 ofan idler gear 2I mounted for rotation on a stub shaft 22 which may besecured in the front Wall I5 by a. nut or the like, the idler gear 2Ibeing lubricated by a grease cup or other lubricating means 24.

The idler gear 2I is mounted eccentrically of the rotor I1 and as iscommon in this type of pump, a partition or baffle 25 is providedbetween the ends of the idler gear teeth 29 and the internal surface ofthe rotor teeth I8 in the area in which the idler is spaced from therotor.

A rotor of the type heretofore used in these pumps is shown by way ofillustration in Fig. 2 and comprises a solid cast or forged body 23having a drive shaft 21 secured thereto by a key or the like 28, theteeth 29 being formed by an end mill operating vertically to machine theside faces 30 to the contour desired. It will be noted from A rotorconstructed in accordance with this invention is shown in detail inFigs. 3 and 4 in which the plate I9 is secured to a drive shaft 3| by akey or the like 32 and a collar 33 welded or brazed to the plate I9 at34. Plate I9 serves to support and drive a plurality of gear teeth I8and these teeth are formed with longitudinal surfaces 35 of the propercontour for engagement with teeth 20 of the idler gear 2|. Teeth I9 maybe machined separately in any desired manner, such as by use of a formcutter on a planer or milling machine and a single individual tooth I3is shown in perspective in Fig. 5 and as will be seen from an inspectionof this figure the tooth is provided at its inner end with a reducedcylindrical portion 36 adapted for reception in an aperture 31 in plateI9. Reduced portion 35 is of such a diameter as to have a relativelytight fit in aperture 3'! thus properly positioning the tooth I9coaxially with the shaft 3 I.

The necessary number of teeth I8 are machined and positioned in theircorresponding recesses 31 in plate I9 whereupon the loosely assembledrotor is inserted in a jig or fixture to properly orient the teeth sothat the surfaces 35 thereof will be in position to properly engageteeth 20 of idler gear 2| and while held in the assembly jig a hole 38is drilled radially into the peripheral edge 33 of the plate I9 throughthe reduced portion 36 of the tooth I9 and into the material of theplate at the opposite side of the aperture 31. Tightly fitting dowelpins 40 are then driven into these holes to lock the teeth I8 inposition in the plate I9. The rotor is then removed from the assemblyjig or fixture and the teeth I8 permanently secured in place by brazing,welding or otherwise adequately securing the reduced portion 36 to theplate I9 at 4 I.

It will be noted from an inspection of Fig. 4 that the teeth I8 areconsiderably longer than twice the minimum distance between adjacentteeth and as a matter of fact these teeth may be made any desired lengthwithin the strength characteristics of the material employed for theteeth. Consequently a rotor with considerably longer teeth than thoseheretofore possible may be constructed and utilized in a rotary pump ofthe type described above to materially increase the capacity thereofwithout increasing the diameter and only slightly increasing the lengththereof.

It has been found that pumps utilizing rotors constructed in accordancewith this invention, while having a greater capacity than heretoforepossible within the same dimensions also possess much longer wearingqualities in that the tooth area in contact with the fluid being pumpedis considerably greater, thus reducing the wear per unit area andfurthermore the load is distributed over a considerably larger arearather than being concentrated thus further reducing strain and wear.

It will thus be seen that by this invention there has been provided arelatively simple and eificient rotor for the purpose intended which iseconomical to produce and which exhibits increased wearingcharacteristics, thus resulting in the production of pumps of relativelysmall weight and dimensions yet having high pumping capacities andrelatively long life.

It will be obvious to those skilled in the art that various changes maybe made in the invention without departing from the spirit and scopethereof and. therefore the invention is not limited by that which isshown in the drawings and described in the specification but only asindicated in the appended claims.

I claim:

1. A rotary pump comprising a casing, a driven toothed rotor rotatablymounted in said casing and an idler gear rotatably mounted in saidcasing and having teeth meshing with the teeth on said rotor, said rotorcomprising an end plate, a driving shaft secured to said plate centrallythereof and extending from one side only, a plurality of apertures insaid plate disposed in a circle adjacent the outer edge thereof, aplurality of gear teeth having reduced extensions disposed in saidapertures and extending axially of said plate to form a hollow gear,said extensions being secured in said apertures by dowels and brazing,the length of said teeth being greater than twice the minimum distancebetween tWo adjacent teeth.

2. A rotary pump comprising a casing, a, driven toothed rotor rotatablymounted in said casing and an idler gear rotatably mounted in saidcasing and having teeth meshing with the teeth on said rotor, said rotorcomprising a driven end plate and a plurality of teeth removably securedto said plate and extending axially thereof the length of said teethbeing greater than twice the minimum distance between two adjacentteeth.

3. In a rotary pump having a casing, a hollow gear type rotor and anidler gear meshing with said rotor, the improvement consisting inproviding said rotor with individually formed and removably attachedteeth of a length greater than twice the minimum distance between twoteeth whereby the capacity of said pump may be varied by utilizingrotors having teeth of different lengths.

4. A method of making a hollow gear type pump rotor comprising providingan end plate, formin a plurality of apertures in said plate disposed ina circle adjacent the outer edge thereof, machining a plurality of teethof the desired contour and of a length greater than twice the minimumdistance between two adjacent teeth, forming a reduced extension on oneend of each tooth, assembling said teeth with said plate by insertingsaid extensions in said apertures, accurately positioning and holdingsaid teeth while inserting dowels through said extensions into saidplates and finally brazing said extensions to said plate.

5. A method of making a hollow gear type pump rotor comprising providingan end plate, forming a'plurality of apertures in said plate disposed ina circle adjacent the outer edge thereof, machining a plurality of teethto the desired contour and of a length to provide the desired pumpcapacity, forming a reduced extension on one end of each tooth,assembling said teeth with said plate by inserting said extensions insaid apertures, accurately positioning and holding said teeth whileinserting dowels through said extensions into said plate and finallybrazing said extensions to said plate.

JULIAN B. THOMAS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

